function y = p0(m, rho, B)

s = 0;
for k = 0:1:m
    s = s + ((m * rho)^k) / factorial(k);
end

p = ( ((m * rho)^m) / factorial(m) ) ;
s2 = 0;
for k = 1:1:B-m
    s2 = s2 + rho^k;
end

y = s + p * s2;
y = 1 / y;

end